JPS63245024A - In-band signal device - Google Patents

Abstract

PURPOSE:To attain efficient level adjustment at the reception side by extracting a signal of a prescribed frequency from a received signal and detecting a detection signal when an output signal level is a prescribed level or over so as to apply the control bringing the output signal to a prescribed level. CONSTITUTION:In receiving a test signal, a reception section 61 of a transmission/reception station 121 extracts only the test signal of a prescribed frequency from the received signal, the signal is rectified into a DC and retards it for a prescribed time and supplies the result to a noninverting input of a comparator 5. When the voltage of the signal after the delay is larger than the voltage applied to the inverting input by means of resistance division, the comparator outputs a detection signal, resulting that an output signal of a reception circuit 4 is supplied to a level monitor circuit 12. In such a case, the level monitor circuit 12 monitors the output signal of the reception circuit 4 to control the attenuation of a variable attenuation circuit 3. Thus, the level of the reception signal is made constant and the level adjustment at the reception section is executed efficiently.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an in-band signal device that performs communication using signals in the audio frequency band, and in particular, the level of the received signal on the receiving side is controlled by remote control from the transmitting side. This invention relates to a device that automatically performs adjustment.

[Conventional technology]

FIG. 2 shows a block diagram of a conventional in-band signaling device.
．． 120 each includes a transmitting section 50 having a transmitting circuit 2, and a receiving section 60 having a receiving circuit 4 and a resistive attenuator 13.

The level of the received signal is adjusted as follows.For example, when adjusting the transmitting/receiving station 120, first input a test signal having a frequency different from that of the signal for communication from the terminal 4WS. Measure the level of the received signal at terminal 4WR.

Then, the resistance attenuator 13 is manually adjusted so that this signal level becomes a predetermined value.

[Problem that the invention seeks to solve]

As described above, conventional in-band signal devices have the drawback that when adjusting the level of a received signal, manual intervention is always required on the receiving side, and level adjustment cannot be performed efficiently.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks and provide an in-band signal device that can efficiently adjust the level of a received signal.

[Means for solving problems]

The present invention provides an in-band signal device that performs communication using a signal in an audio frequency band, which includes: a transmitter that sends a signal at a predetermined frequency to a transmission path; and a signal at the predetermined frequency from a signal received through the transmission path. a signal detection circuit that outputs a detection signal when the output signal level of the bandpass filter is equal to or higher than a predetermined level; a variable attenuation circuit to attenuate; and a control signal that monitors the level of an output signal of the variable attenuation circuit and sets the output signal of the variable attenuation circuit to a predetermined level when the signal detection circuit outputs the detection signal. The present invention is characterized by comprising a level monitoring circuit that outputs an output to the variable attenuation circuit.

〔Example〕

Next, one embodiment of the present invention will be described.

FIG. 1 shows a block diagram of this embodiment. This in-band signaling device is composed of transmitting/receiving stations 111 and 121, each of which is equipped with a transmitting section 51 and a receiving section 61. The transmitter 51 of the transmitter/receiver station 111 and the receiver 61 of the transmitter/receiver station 121 are connected by a transmission path 131, and the transmitter 51 of the transmitter/receiver station 121 and the receiver 61 of the transmitter/receiver station 111 are connected, respectively.

The oscillator l of the transmitter 51 outputs a test signal having a predetermined frequency different from that of the signal used for communication. The transmitting circuit 2 amplifies the signal input to the terminal 4WS and sends it to the transmission line 131. The switch 15 inputs the test signal from the oscillator 1 to the transmitting circuit 2 when turned on.

The receiving section 61 has a variable attenuation circuit 3 and a receiving circuit 4.
The variable attenuation circuit 3 changes its resistance value in response to a control signal from a level monitoring circuit 12, which will be described later, and appropriately attenuates the signal received from the transmission path 131 and outputs the signal. Receiving circuit 4
amplifies the signal from the variable attenuation circuit 3 and outputs it from the terminal 4WR. When the switch 11 is on, the level monitoring circuit 12 monitors the level of the output signal of the receiving circuit 4 through this, and varies a control signal for changing the resistance value of the variable attenuation circuit 3 so that this level becomes a predetermined value. It is applied to the attenuation circuit 3. The switch 11 is turned on or off by a relay 10, which will be described later.

The signal from the transmission line 131 is input to the variable attenuation circuit 3 described above, and is also input to the bandpass filter 7. This filter extracts only the test signal of the predetermined frequency from the received signal. The rectifier circuit 6 rectifies the signal from the bandpass filter 7 and converts it into direct current, and the delay circuit consisting of a resistor 8 and a capacitor 9 delays the signal converted into direct current by a predetermined time. Comparator 5 receives the delayed signal at its non-inverting input;
When the voltage value is larger than the voltage value given to the inverting input by resistance division, a detection signal is output. The base of transistor 16 is connected to the output of comparator 5, the emitter to ground, and the collector to one terminal of relay 10, the other terminal of which is connected to the +15V power supply. Therefore, when the comparator 5 outputs a detection signal, the base current is supplied to the transistor 16, the transistor 16 is turned on, and current flows through the relay 10. At this time, the switch 11 is turned on. The components from the rectifier circuit 6 to the comparator 5 constitute a signal detection circuit that detects the test signal included in the received signal.

Next, the operation will be explained. Terminal 4WS of either transmitting/receiving station
The signal input to is amplified by the transmitting circuit 2 and sent to the transmission line 131. The signal reaching the other station via the transmission path 131 is attenuated by the variable attenuation circuit 3 and input to the receiving circuit 4.

The received signal is amplified here with a predetermined amplification factor, and is sent to terminal 4WR.
is output from. Since the attenuation rate of the variable attenuation circuit 3 is adjusted as described later, the level of the received signal output from the terminal 4WR is always constant.

Next, the level adjustment of the received signal will be explained. For example, when adjusting the level of the transmitting/receiving station 121, first the transmitting/receiving station 1
At step 11, the switch 15 of the transmitter 51 is turned on. As a result, a test signal of a predetermined frequency from the oscillator 1 is input to the transmitting circuit 2 via the switch 15. The transmitting circuit 2 amplifies this test signal and then sends it to the transmission line 131.

The receiving section 61 of the transmitting/receiving station 121 receives the test signal sent through the transmission line 131. The bandpass filter 7 extracts only the test signal of a predetermined frequency from this received signal and inputs it to the rectifier circuit 6. A rectifier circuit 6 rectifies the signal from the bandpass filter 7 and converts it into direct current, and a delay circuit consisting of a resistor 8 and a capacitor 9 delays this signal converted to direct current by a predetermined time and then compares the signal. 5 to the non-inverting input of the converter 5. Due to this delay, only signals that continue for a predetermined period of time or more are input to the comparator 5 as test signals, thereby preventing malfunctions due to noise or the like. Comparator 5 outputs a detection signal when the voltage value of the delayed signal input to the non-inverting input is greater than the voltage value given to the inverting input by resistance division. That is, when a signal that has a predetermined output and continues for a predetermined time or more is input to the receiving section 61, a detection signal is output from the comparator 5 as a test signal has been sent.

When the detection signal is output, a base current flows through the transistor 16, which turns on the transistor 16, and a current flows through the relay 10, turning on the switch 11. As a result, the output signal of the receiving circuit 4 is input to the level monitoring circuit 12.

At this time, the level monitoring circuit 12 outputs a control signal to the variable attenuation circuit 3, monitors the output signal of the receiving circuit 4, and controls the amount of attenuation of the variable attenuation circuit 3 according to the level. That is, when the level of the output signal is high, the amount of attenuation of the variable attenuation circuit 3 is controlled to be large, while when the level is low, the amount of attenuation is controlled to be small. As a result, the level of the received signal output from the terminal 4WR is always constant regardless of the level of the input signal.

All the level adjustments in the receiving section 61 are performed automatically in this way, and can be carried out efficiently without any manual intervention.

Incidentally, the level monitoring circuit 12 monitors the output signal of the receiving circuit 4, which means that the output signal of the variable attenuation circuit 3 is monitored through the receiving circuit 4. Further, controlling the level of the output signal of the receiving circuit 4 to a predetermined level is equivalent to controlling the level of the output signal of the variable attenuation circuit 3 to a predetermined level.

〔Effect of the invention〕

As explained above, the in-band signaling device of the present invention is an in-band signaling device that performs communication using signals in the audio frequency band, and includes a transmitter that sends a signal of a predetermined frequency to a transmission path, and a transmitter that sends a signal of a predetermined frequency to a transmission path, and a signal that is received through the transmission path. a bandpass filter that extracts a signal of a predetermined frequency from a signal received by the bandpass filter, a signal detection circuit that outputs a detection signal when the output signal level of the bandpass filter is equal to or higher than a predetermined level, and a signal received through a transmission line. a variable attenuation circuit that attenuates the output signal based on a control signal, and monitors the level of the output signal of the variable attenuation circuit, and sets the output signal of the variable attenuation circuit to a predetermined level when the signal detection circuit outputs a detection signal. and a level monitoring circuit that outputs a control signal to the variable attenuation circuit.

As a result, all level adjustments on the receiving side can be performed automatically and efficiently without human intervention.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional in-band signal device. 1... Oscillator 2... Transmission circuit 3... Variable attenuation circuit 4... Receiving circuit 5... Comparator 6... Rectifier circuit 7. ... Bandpass filter 8 ... Resistor 9 ... Capacitor 10 ... Relay 11, 15 ... Switch 12 ... Level monitoring circuit 16 ...・Transistor 51...Transmission unit 61...Reception unit 111, 121...Transmission/reception station 131...Transmission line 4WS, 4WR...Terminal

Claims (1)

[Claims] (1) An in-band signaling device that performs communication using signals in the audio frequency band, which includes a transmitter that sends a signal at a predetermined frequency to a transmission path, and a signal at the predetermined frequency from a signal received through the transmission path. a bandpass filter for extraction, a signal detection circuit that outputs a detection signal when the output signal level of the bandpass filter is equal to or higher than a predetermined level, and attenuates the signal received through the transmission path based on a control signal. a variable attenuation circuit that monitors the level of the output signal of the variable attenuation circuit, and sends the control signal to set the output signal of the variable attenuation circuit to a predetermined level when the signal detection circuit outputs the detection signal; An in-band signal device comprising: a level monitoring circuit that outputs to a variable attenuation circuit.